(INDIANAPOLIS) - New research shows that more teenagers are smoking tobacco using a hookah, and one doctor says some of them believe it doesn't hurt them.

A study published in the journal Pediatrics showed that one out of five high school seniors said they had smoked from a hookah, the water pipes that have been used for centuries in the Middle East. They are increasingly popular in bars in the U.S. - hookah bars are exempt from the smoking ban in Indianapolis as well as Indiana's statewide smoking ban.

"There has been a decrease in cigarette smoking among teenagers, but that has coincided with an increase with such things as e-cigarettes and hookah," said Dr. Michael Busk, system executive with St. Vincent Health, Wellness and Preventive Care Institute.

Busk, who also serves on the board of the American Lung Association, also says there is a mistaken impression that, since the smoker's lips aren't touching the tobacco, hookah smoking isn't as bad for you. In fact, another recent study published the journal Nursing Research showed that a majority of teens who have tried hookah believe it is a safe way to smoke.

Busk says calculations from advisers to the Lung Association found otherwise.

"You are burning charcoal and tobacco, which means the smoke contains high levels of metals and cancer-causing chemicals," Busk said. "You are inhaling much more deeply into your lungs, and you are puffing more times. An average cigarette is about 20 puffs. An average hookah session is around 200 puffs."

The Food and Drug Administration does not regulate hookah smoking, though it is under consideration. Busk says that doesn't help, nor does the flavoring of hookah tobacco, which attracts younger smokers.

"Green apple, coconut, and more recently I even found a bubble gum flavor of hookah tobacco, apparently marketed toward an even younger generation," Busk said.

While most hookah bars have age restrictions for customers, the lack of FDA regulation means that anyone can buy a hookah pipe and tobacco, especially online.